Anorexia nervosa (AN) is a serious and often chronic psychiatric disorder with a high likelihood of medical complications and a high mortality rate. Very little is known about risk factors for AN and even less is known about factors which serve to maintain the disorder and promote potential chronicity. Recently there has been an increased interest in the role of cognitive-emotional factors, in the maintenance function of this disorder. In individuals with high degrees of negative affect, anorexic behaviors may serve to reduce anxiety and other negative mood states, which negatively reinforce the symptoms. While cognitive-emotional variables may play a significant role in the onset and maintenance of AN, very little is known about the relationship between these variables and anorexic symptoms on a daily, or momentary basis. Most studies of the psychopathology and pathophysiology of AN rely on cross-sectional designs with retrospective recall of variables of interest. It is well documented that retrospective recall of mood variables can be severely distorted, thus risking the validity of studies of mood-eating disorder behavior relationships. Research designs are needed which allow a prospective longitudinal assessment of the relationship of maintenance variables and anorexic symptoms. Furthermore, research is needed to better understand the momentary relationship among stressful environmental stimuli, mood and cognitive variables, and anorexic behavior. Ecological Momentary Assessment (EMA) is a research methodology that relies on assessing subjects several times per day for a period of several days to several weeks in order to gain a clearer understanding of the momentary relationship between environmental events, psychological constructs, and behaviors. Furthermore, data collection is now possible through the application of Palm Top computers which allows an immediate assessment of relevant variables in the subject's natural environment with electronic safeguards to ensure that data is collected at designated times. EMA methodology would be an excellent approach to understanding the relationship between environment and anorexic behavior, along with psychological mediators such as cognitive and emotional variables.